Changing the color of keratinous fibers, in particular hair, represents an important area of modern cosmetics. The appearance of the hair may thus be adapted to current fashion trends and to the person's individual preferences. Various options are known to those skilled in the art for changing the color of the hair. The hair color may be temporarily changed by using direct dyes. In the process, dyes which are already formed diffuse from the coloring agent into the hair fiber. Although coloration using direct dyes involves little damage to the hair, it is disadvantageous that the colorings obtained with direct dyes are not very durable and wash out quickly.
If the consumer desires a long-lasting color result or a shade that is lighter than his/her original hair color, oxidative color-changing agents are customarily used. For permanent, intense colorations having appropriate fastness properties, so-called oxidation dyes are used. Such coloring agents customarily include oxidation dye precursors, so-called developer components and coupler components, which form the actual dyes with one another under the influence of oxidizing agents. Oxidation dyes are characterized by long-lasting color results.
Extensive prior art already exists with regard to oxidative coloring agents. Considerable testing has been conducted, in particular for optimizing the color intensity and fastness properties of fashionable shades.
However, despite the large number of optimization tests already carried out, there is still a need for improvement of the color intensity of oxidatively dyed keratin fibers, in particular when they are colored in a fashionable reddish shade. In particular, the color intensity and shade outcome of copper shades cannot yet be considered to be optimal.
The wash fastness of a color shade is understood to mean the change in color of the hair strands colored with this shade under the influence of multiple hair washings. This change in color may involve a shift of the color toward another hue, or also lightening of the coloring. Both changes in color are equally undesirable to the user. Color shades with good wash fastness experience little or no change in color, even after repeated hair washings. The hair washing may take place using a shampoo, a conditioning shampoo, or a conditioner.
An improved shade outcome and enhanced brilliance are understood, within the framework of the present invention, to mean that the copper shade that can be achieved with the agents impart overall a more fashionable—i.e., more intense and reddish—impression without a brown tint. The color richness can be quantified in colorimetric measurements, by determining the chroma value (C).
Keratinous fibers can be dyed in copper tones when a specific combination of (A) the developer 1-(2-hydroxyethyl)-4,5-diamino pyrazole and (B) the coupler 2,6-dihydroxy-3,4-dimethylpyridine is used in the coloring agents. Corresponding agents are known, for example, from EP 1488783 A1. In these formulations known from the prior art, however, there is always at least one anionic surfactant present in the ready-to-use oxidative coloring agent.
Desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.